Metal allergy has been implicated as a cause of complications such as pain, fluid accumulation, and skin reactions in some individuals bearing metallic implants. The cause and effect of these reactions is unknown; does pre-existing allergy cause loosening of the device and then the symptoms; does the device loosen and then the allergic individuals develop symptoms? Similarly does the presence of the device cause the allergy? A prospective study is proposed to determine which patients are allergic to metals prior to joint arthroplasty surgery, which acquire an allergy after implant surgery, and what effect the condition has on the prognosis for the implant. A retrospective study of patients admitted for metallic implant removal is proposed to ascertain the correlation between metal allergy and symptoms associated with the implant. An in vitro test of T-lymphocyte production production of leukocyte migration inhibition factor in response to metal salts will be used to document the allergic conditions. An animal study is also proposed in which metal allergy will be induced before and after implantation of metal screws, and the effects of the allergic reaction at the site of implantation studied.